The novel takes place in the 11th Century Middle East, where the charismatic leader of a radical Islamic sect, known as the Ismailis, manipulates and controls his followers through a combination of religious indoctrination, drugs, and the promise of paradise. The leader creates a literal paradise within the walls of his fortress, Alamut, in order to convince his followers that they are experiencing the afterlife. The story explores themes of power, manipulation, and the nature of faith.